CORD-706: Worked around an ssh/ssh proxy bug that would cause ansible's
ssh to remember a failed DNS lookup, and prevent the proxy command from
working.

Change-Id: Icc2d24532a6fc09bea214ed4f9266e7f9931ecc6
diff --git a/xos/synchronizers/base/ansible_helper.py b/xos/synchronizers/base/ansible_helper.py
index d39e45a..6cf990d 100644
--- a/xos/synchronizers/base/ansible_helper.py
+++ b/xos/synchronizers/base/ansible_helper.py
@@ -139,6 +139,9 @@
         except:
             proxy_ssh = True
 
+    if (not ssh_ip):
+        raise Exception('IP of ssh proxy not available. Synchronization deferred')
+
     (opts, fqp) = get_playbook_fn(opts, path)
     private_key_pathname = fqp + ".key"
     config_pathname = fqp + ".config"